The present invention relates to vehicle occupant safety systems, and more particularly, to a vehicle occupant proximity sensor for use with a vehicle occupant safety system.
Vehicle occupant safety systems that are activated in response to a vehicle crash for purpose of mitigating occupant injury are well known in the art. A vehicle may contain automatic safety restraint actuators such as front and side air bags, seat belt pretensioners, and deployable knee bolsters. The occupant protection system may further include a collision/crash sensor for sensing the occurrence of a vehicle crash and for providing an electrical signal indicative of the crash severity.
Several known occupant protection systems include an occupant position sensor that senses the position of the occupant with respect to an associated inflatable protection module. The occupant position sensor for such a system could be an ultrasonic sensor, an infrared sensor, and a capacitive sensor, and/or a weight sensor. A controller, which is connected to the sensors, controls the inflatable protection module in response to the sensed position of the occupant. In response to the sensed occupant position, one or more deployment aspects of the air bag may be adjusted. A protection system with adjustable aspects of deployment is commonly referred to as an “adaptive” protection system. Specifically, if the occupant is positioned in a position such that deploying the air bag will not enhance protection of the occupant, it may be desirable to suppress actuation of the occupant protection module. An occupant who is very near the protection module is referred to as being within an occupant out-of-position zone. Deploying the air bag for an occupant who is within the occupant out-of-position zone may not enhance protection of the occupant.
In any case the determination of occupant's position is an important part of adaptive occupant protection system. There are several types of proximity sensors, such as ultrasonic sensor, a video sensor, a capacitive sensor, and an infrared sensor. Different obstacles such as a map, a book, or a newspaper could occlude signals from ultrasonic and video sensors. A lighter or cigarette could blind an infrared sensor.
This invention is based on the conductivity of the human body. This phenomenon allows the occupant to be used as a transmitting antenna, determining his/her position within a defined space by measurement of electromagnetic values induced on a set of receivers.